Quantitative behavioral experiments yield measures of performance in electrolocation of objects in weakly electric fish. Electrolocation serves functions of orientation and assessment of the environment. Electrolocation is achieved on the basis of sensory feedback from electrical signals emitted by the same animal, comparable to echolocation in the realm of sound. In both instances sensory feedback may be contaminated by signals from other individuals and particular behavioral strategies to minimize jamming have evolved in electric fish. Electric fish can be classified into wave- and pulse-species. Electrical discharges in the first group are of a duration similar to the interval between discharges and thus follow each other in a continual sinusoidal pattern. Electrical discharges in the second group are of very short duration compared to the interval between discharges. These two types of electric fish both occur within the African Mormyriformes and the South American Gymnotoidei, two widely separated groups of fish, and thus must have evolved in a convergent manner. Functional advantages and adaptive significance of wave systems on the one hand and pulse-systems on the other will be investigated. Since both types evolved in a polyphyletic manner, comparative quantitative studies across different groups of electric fish should yield insight into their evolution and adaptation. I plan to perform behavioral experiments in coordination with neurophysiological studies carried out in Prof. T.H. Bullock's group. BIBLIOGRAPHIC REFERENCES: Heiligenberg, W.: Electrolocation and Jamming Avoidance in the Electric Fish Gymnarchus niloticus, J. Comp. Physiol. 103: 55-67, 1975. Bullock, Th. H. Behrend, K. and Heiligenberg, W.: Comparison of the Jamming Avoidance Responses in Gymnotoid and Gymnarchid Electric Fish: A case of convergent evolution of behavior and its sensory basis, J. Comp. Physiol. 103:97-121, 1975.